Correlation between podocyte excretion and proteinuria in diabetic nephropathy patients

Abstract

Objective To observe the podocyte injury in diabetic nephropathy (DN) patients by identifying the urinary podocytes and the situation of detached podocytes in glomeruli and to demonstrate the correlation between podocyte excretion and proteinuria, blood glucose, serum creatinine in different phases in DN patients. Methods Urinary podocytes and the podocalyxin (PCX) expression state of podocytes in glomeruli were identified and observed by indirect immunofluorescent method. The DN patients were divided into three groups according to the volume of proteinuria, namely small, medium and large volume proteinuria groups. The podocytes in the urine of every group were calculated. The DN patients were divided into five groups according to the chronic kidney disease (CKD) phases, then the positive podocytes in urine were calculated. Meanwhile, the 24-hour protein in urine, fasting blood glucose (FBG) and the serum creatinine of DN patients were tested. The correlations among the proteinuria, serum creatinine, FBG and the number of positive podocytes in the urine of DN patients were statistically analyzed. Results Urinary positive podocytes were found in 88% of the patients with DN, whereas podocytes were found in 0% of patients with minimal changed disease (MCD) and healthy cases. The expression of PCX was absent in DN patients. In contrast, PCX was expressed integrally in MCD patients. The positive podocytes was 1.49±0.95/ml in small-volume proteinuria group, 2.15±0.70/ml in the medium-volume proteinuria group, and 3.48±1.27/ml in the large-volume proteinuria group. There was no significant difference between the small- and medium-volume proteinuria groups, and there were significant differences between other groups ( P<0.05). The positive podocyte number tended to increase as proteinuria was increased. By Pearson analysis, the correlation between podocyte number and proteinuria was positive statistically. The difference of the number of positive podocytes in urine from different groups of DN patients, CKD I - V group was significant statistically. The correlation between serum creatinine of CKD I - III group and positive podocytes in urine was positive statistically. The correlation between serum creatinine of CKD IV - V group and positive podocytes in urine was not significant statistically. The correlation between FBG and positive podocytes in urine was not significant either. Conclusion The mechanism of the podocyte injury in DN patients is present. The podocyte injury in DN may positively correlate to proteinuria and serum creatinine of CKD I - III DN patients, but not to the FBG and serum creatinine of CKD IV - V patients.